The evolution of the NFL:
Take a look at how the NFL has evolved from its humble roots, and the efforts being made to ensure it continues to grow.

The NFL and the Colts announced Friday that outside linebacker Robert Mathis was suspended four games for violating the league's performance-enhancing drug policy.

Mathis released a statement through NFL Media Insider Ian Rapoport in which Mathis said the failed test came from taking fertility drugs. He admitted that he made the mistake of not checking with the NFL or NFL Players Association about whether the drugs would present a problem for drug testing.

"The union has worked very closely with me to present all of the facts and medical records for consideration of discipline that does not include a suspension because of the unique facts of my case, but the Commissioner refused the request," Mathis said.

Rapoport reported the drug was Clomid, citing a source close to Mathis. However, the drug Mathis tested positive for is "not approved by the FDA for fertility in males and is a performance-enhancing drug that has been prohibited for years," said NFL spokesperson Greg Aiello in a statement obtained by NFL Media's Albert Breer.

Mathis and his wife had twins in 2012, and they are expecting another baby this year. Mathis apologized to the team, his fans and his teammates. His coach spoke on his behalf on Saturday.

"With regards to the recent suspension of Robert Mathis, we're going to honor the League's policy as far as confidentiality goes," Colts coach Chuck Pagano said. "We certainly understand the severity of this situation, but as we've done many, many times before in our short stint here, we'll get through this. We'll come together as a team. We'll come together as a family. We'll come together as an organization and we'll get through this. We love and respect Robert Mathis. He's a horseshoe guy, he's a pillar guy, and like I said before, we've got his back. Everybody in this organization has his back and we'll get through this and at the end of the day, we'll all be better for it."

Mathis, who led the NFL in sacks with 19.5 last season, will be eligible to return to the team's active roster on Sept. 29 after the team's Week 4 game versus Tennessee. Mathis will miss the season opener against the Denver Broncos, a rematch against his old teammate Peyton Manning. (Mathis delivered the game-changing sack of Manning in last year's upset against Denver.) Mathis will also miss games against the Philadelphia Eagles and Jacksonville Jaguars.

The Colts' defense had plenty of questions even before this news. Indianapolis has struggled to find a secondary pass rusher behind Mathis and gave up 87 points in two playoff games last season.